Early detection of breast cancer is critical to patient outcome. The specific aim of this program is to demonstrate dual-energy contrast-enhanced digital subtraction mammography (DE-CEDSM) using a proprietary quasi-monochromatic x-ray source (QMS) technology currently under development at SRL. Using a broadband source, DE-CEDSM has already been demonstrated to enhance breast tumors that are otherwise mammographically occult. A promising clinical demonstration of DE-CEDSM has been recently performed by our collaborator Dr. John Lewin of the University of Colorado Health Sciences Center. The use of optimized quasi-monochromatic radiation will significantly improve the sensitivity such that DE-CEDSM will be able to detect smaller tumors that would otherwise be masked by tissue and fat variations in the breast. SRL's QMS technology is currently under development for improving angiographic images. In this Phase I project, we will quantify the improvements in image quality and reduction of dose that can be achieved by using a QMS for mammography as compared to using a broadband source as has been demonstrated by Dr. Lewin. Preliminary calculations show that the improvements should be significant with the radiation dose requirement dropping by half and suppression of tissue features, a critical feature of the technique, improving as well. Following a successful Phase I program, the Phase II effort will concentrate on building and testing a prototype that integrates a QMS with a full-field digital mammography system. This technology will allow for successive real-time subtracted contrast-enhanced mammograms using industry standard iodinated contrast agents. Contrast agent can be administered prior to breast compression, allowing for adequate perfusion of breast tissue. The dual-energy method will allow for viewing suspected lesions from multiple angles as well as for measuring contrast uptake and dispersion over time. Measurements of contrast density can be absolutely calibrated, giving additional diagnostic information to the radiologist.